flask-sqlalchemy with_entities和关系 [英] flask-sqlalchemy with_entities and relationships

问题描述

我只想从模型中选择几列来加快查询速度，但是我要选择的一列来自关系.

I want to select only a couple columns from my model to speed up the queries, but one of the columns I want to select is from a relationship.

型号:

class OpenChromatinRegion(db.Model):
    ...
    gene_id     = db.Column(db.Integer, db.ForeignKey("gene.id"), nullable=False, index=True)
    gene        = db.relationship("Gene", back_populates='open_chromatin_regions')

class Gene(db.Model):
    id          = db.Column(db.Integer, primary_key=True)
    ENSEMBLID   = db.Column(db.Integer, index=True, unique=True, nullable=False)
    ...

查询:

q = OpenChromatinRegion.query.with_entities(Gene.ENSEMBLID, ...)...

我如何使用我以前尝试过的.with_entities(OpenChromatinRegion.gene.ENSEMBLID)的flask-sqlalchemy正确地从OpenChromatinRegion中仅选择几列，但是那也不起作用.使用这种语法，我没有收到错误，但是请求超时.

How do I properly select only a couple columns from OpenChromatinRegion using flask-sqlalchemy I previously tried .with_entities(OpenChromatinRegion.gene.ENSEMBLID) but that didn't work either. With this syntax, I don't get an error but the request times out.

推荐答案

您需要进行加入:

q = OpenChromatinRegion.query.join(OpenChromatinRegion.gene) \
                             .with_entities(Gene.ENSEMBLID)

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